THEORIES AS TO ORIGIN, ANCESTRY, AND ADAPTIVE RADIATION 



781 



Figure 707. — Outlines of the body form of the perissodactyls drawn to the same scale 



The largest known member of each family is selected for comparison. The aiumals are grouped according to their natural relation- 

 ships, indicated especially by the pattern of the molar teeth, as follows: 



Ehinocerotoid group: A, Melamynoion, family Amynodontidae. graviportal aquatic rhinoceros, lower Oligocene; B, Byracodon, 

 family Hyracodontidae, cuisorial rhinoceros, lower Oligocene; C, Ceratolherium simum, family Rhinocerotidae, living white 

 rhinoceros, graviportal. Tapiroid group: D, Tapirus terrestris, family Tapiridae, living tapir. 



Hippoid group: B, Palaeotherium, family Palaeotheriidae, mediportal, lower Eocene; F, Equus przewalshi, family Equidae, living 

 horse, cursorial. 



Chalicotheroid group: G, Moropus, family Chalicotheriidae, clawed perissodactyl, lower Miocene. 



Titanotheroid group: if, Bwvtotherium plalyceras, family Brontotheriidae, graviportal, lower Oligocene. 



